"Fewer residents recognized that trees can cool neighbourhood temperatures generally," said Jason Byrne of Griffith University, Australia. "Many did not appear to make the connection between greener neighbourhoods, cooling and lower electricity expenses. Few respondents expressed concerns about greening."

Byrne and colleagues conducted the study, one of the first of its kind outside North America, to examine thermal inequity. They sent a survey to 1921 households in the relatively disadvantaged Upper Coomera suburb of Gold Coast City in Queensland, receiving 230 replies.

"My team and I are really concerned about the impacts of climate change," said Byrne. "We know that these impacts will disproportionately affect low income earners and people of colour. This is because marginalized and disadvantaged populations often lack the financial wherewithal, political connections and/or opportunities to live in places that are free from environmental hazards like floods (a situation termed environmental injustice)."

Upper Coomera street scene
Upper Coomera street scene



Heat is also a good example of environmental injustice, according to Byrne. "Often, low income and disadvantaged communities are confined to housing that is poorly constructed or which – by virtue of being affordable – lacks large areas of greenery, which can keep neighbourhood temperatures cooler," he added. "If residents' only option is to run an air-conditioner for cooling, they may find themselves having to make difficult choices between paying high electricity bills, paying for school books and supplies and/or being able to afford healthy food."

Byrne and colleagues worked with their local council to find out if residents of one such community would respond favourably to initiatives to make their neighbourhood greener – such as tree planting in parks and on street verges – as a way to cool urban temperatures, and whether they had any concerns about urban greening.

"Some of our results were unexpected," said Byrne. "Governments in Australia across all levels – federal, state and local – have been slow to respond to the challenges posed by climate change. There has also been a strong element of climate change denial within some sectors of the Australian population." So the team thought many residents would believe that climate change was not real, or would be unconcerned. "Consequently, we expected to find that residents did not favour greening initiatives," Byrne explained. "Instead, what we found was that the majority of residents we surveyed strongly believed that climate change was real and the majority were very concerned about this."

The team was also surprised by the high level of support amongst residents for urban greening. "This means that local governments and land and property developers can now start to move forward on finding better ways to integrate more greenery into urban and suburban residential areas," said Byrne. "Councils can be increasingly confident that urban greening initiatives will likely be favourably considered by local residents."

The researchers had thought that residents may have urban greening concerns about safety, perceptions of higher maintenance burdens or because the greening might impact recreational activities in local parks. The chief concern for residents, the survey revealed, was increased maintenance costs due to trees.

Now the team needs to find the right tree species for the right location. "We need to undertake research on trees that grow well in urban areas in different climatic zones," said Byrne. "And we need to find a palette of species that will not impose maintenance burdens on residents or local governments, such as uplifting pavements or dropping branches on houses during storms. We also need to find tree species that will not block winter sunshine to dwellings or shade rooftop photovoltaic solar installations, or have health implications such as causing asthma."

Ideally, the trees would also enhance endemic biodiversity, Byrne says. The team will now work with botanists, civil engineers, local government officers and land and property developers. "We also want to apply the same survey across different climate zones, in different counties and in different cultures to see if the results are consistent," added Byrne. "And we'd like to probe the interconnections between greening to reduce urban temperatures, and levels of physical and mental health among residents. A final topic to explore will be to see if greening increases property values, thus potentially displacing marginalized and disadvantaged residents – a situation called eco-gentrification."

The team reported the findings in Environmental Research Letters (ERL).

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